The goal of the proposed research is to elucidate the cellular events underlying pulmonary surfactant production by type II cells. The investigations focus on the type II pneumocyte-like tumor cell line, A549, with correlative studies to be performed on primary isolates of type II cells. The coordinated biochemical and ultrastructural studies proposed here also employ an organometallic fatty acid analog of palmitate which can be localized by X-ray microprobe analysis and electron microscopy. During this year we have undertaken: (1) biochemical investigations of the pattern of incorporation of radiolabeled precursors into phosphatidylcholine, particulary disaturated phosphatidylcholine, by type II cells; (2) morphological evaluation of A549 cells under different culture conditions; and (3) development of a system for quantitative energy-dispersive X-ray microanalysis of single cells and tissues. The latter has included progress in instrumentation capabilities for spectra acquisition and analysis, the development of techniques for preparation of unfixed, unstained cryosections, and verification and evaluation of the analytical system for quantitation of several elements, viz., Na, P, C1, and K.